2 files changed, 57 insertions, 9 deletions

diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
index 1144cf1c915..4cb3c7bb2a0 100644
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -92,15 +92,26 @@ public:
 
     // Copy initializer elements.
     unsigned i = 0;
+    bool RewriteType = false;
     for (; i < NumInitableElts; ++i) {
       llvm::Constant *C = Visit(ILE->getInit(i));
+      RewriteType |= (C->getType() != ElemTy);
       Elts.push_back(C);
     }
-    
+
     // Initialize remaining array elements.
     for (; i < NumElements; ++i)
       Elts.push_back(llvm::Constant::getNullValue(ElemTy));
 
+    if (RewriteType) {
+      // FIXME: Try to avoid packing the array
+      std::vector<const llvm::Type*> Types;
+      for (unsigned i = 0; i < Elts.size(); ++i)
+        Types.push_back(Elts[i]->getType());
+      const llvm::StructType *SType = llvm::StructType::get(Types, true);
+      return llvm::ConstantStruct::get(SType, Elts);
+    }
+
     return llvm::ConstantArray::get(AType, Elts);    
   }
 
@@ -166,6 +177,7 @@ public:
     // Copy initializer elements. Skip padding fields.
     unsigned EltNo = 0;  // Element no in ILE
     int FieldNo = 0; // Field no in RecordDecl
+    bool RewriteType = false;
     while (EltNo < ILE->getNumInits() && FieldNo < RD->getNumMembers()) {
       FieldDecl* curField = RD->getMember(FieldNo);
       FieldNo++;
@@ -175,22 +187,27 @@ public:
       if (curField->isBitField()) {
         InsertBitfieldIntoStruct(Elts, curField, ILE->getInit(EltNo));
       } else {
-        Elts[CGM.getTypes().getLLVMFieldNo(curField)] =
-            Visit(ILE->getInit(EltNo));
+        unsigned FieldNo = CGM.getTypes().getLLVMFieldNo(curField);
+        llvm::Constant* C = Visit(ILE->getInit(EltNo));
+        RewriteType |= (C->getType() != Elts[FieldNo]->getType());
+        Elts[FieldNo] = C;
       }
       EltNo++;
     }
 
+    if (RewriteType) {
+      // FIXME: Make this work for non-packed structs
+      assert(SType->isPacked() && "Cannot recreate unpacked structs");
+      std::vector<const llvm::Type*> Types;
+      for (unsigned i = 0; i < Elts.size(); ++i)
+        Types.push_back(Elts[i]->getType());
+      SType = llvm::StructType::get(Types, true);
+    }
+
     return llvm::ConstantStruct::get(SType, Elts);
   }
 
   llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) {
-    // FIXME: Need to make this work correctly for unions in structs/arrays
-    CGM.WarnUnsupported(ILE, "bitfield initialization");
-    return llvm::UndefValue::get(CGM.getTypes().ConvertType(ILE->getType()));
-
-    // Following is a partial implementation; it doesn't work correctly
-    // because the parent struct/arrays don't adapt their type yet, though
     RecordDecl *RD = ILE->getType()->getAsRecordType()->getDecl();
     const llvm::Type *Ty = ConvertType(ILE->getType());
 
diff --git a/clang/test/CodeGen/union-init.c b/clang/test/CodeGen/union-init.c
new file mode 100644
index 00000000000..9a515a72d92
--- /dev/null
+++ b/clang/test/CodeGen/union-init.c
@@ -0,0 +1,31 @@
+// RUN: clang -emit-llvm < %s -o -
+
+// A nice and complicated initialization example with unions from Python
+typedef int Py_ssize_t;
+
+typedef union _gc_head {
+	struct {
+		union _gc_head *gc_next;
+		union _gc_head *gc_prev;
+		Py_ssize_t gc_refs;
+	} gc;
+	long double dummy;  /* force worst-case alignment */
+} PyGC_Head;
+
+struct gc_generation {
+	PyGC_Head head;
+	int threshold; /* collection threshold */
+	int count; /* count of allocations or collections of younger
+		      generations */
+};
+
+#define NUM_GENERATIONS 3
+#define GEN_HEAD(n) (&generations[n].head)
+
+/* linked lists of container objects */
+struct gc_generation generations[NUM_GENERATIONS] = {
+	/* PyGC_Head,				threshold,	count */
+	{{{GEN_HEAD(0), GEN_HEAD(0), 0}},	700,		0},
+	{{{GEN_HEAD(1), GEN_HEAD(1), 0}},	10,		0},
+	{{{GEN_HEAD(2), GEN_HEAD(2), 0}},	10,		0},
+};